Shell-less turbo snail?

[Claw Atticas]

Today after feeding my fish, I noticed down at the bottom, one of the turbo snails was eating algae next to another, but only one had a shell!
None of the other fish or cleaner shrimp seem to be picking at him, and he seems to be doing fine, just no shell.
Has anyone else had this problem before? I'm pretty sure the shell will grow back alright if he survives, but I have no idea why he would lose his shell, and also where it went, as I can't find any empty snail shells in my tank.




Ammonia: 0
Nitrites: 0
Nitrates: 0
PH: 8.0
Alkalinity: 180
Temperature 75.5 (Chiller is set to 79)
I could be wrong on these measurements, but they're the best I could find of two tests... PetCo has horrible test strips (They're basically treated sponges, but the water makes the indicator chemicals run everywhere, giving inaccurate readings)

Inhabitants:
2 Pacific Cleaner Shrimp
1 Longnose Butterflyfish
1 Coral Beauty Angelfish
1 Longnose Hawkfish
1 Emerald Mithrax Crab
15 Turbo Snails (Or 14 1/2 if you count the shell-less one)
15 Nassarius Snails
1 Fancy Brittle Star
2 Yellow Sea Cucumbers (Though MIA since I bought them 20 days ago)
(The 2 Percula Clownfish have been in QT for 2 weeks now)

 

[HoCkEyGmC]

idk if thats a turbo, it kinda looks like a big cowrie of some sort. r u sure that its a turbo?

 

[roka64]

It doesn't look like one to me either.
Is there any chance you can get a better pic of it's back?

 

[Innovator]

Looks more like Stomatella varia.

 

[Claw Atticas]

Ah, forgot to show a 'clothed' snail!
Here's a few of the other turbos

 

[Kurt_Nelson]

Agree with Innovator... stomatella's are basically shell-less snails. I think you'll find it might have a little bit of a hard "shield" on its back.

And those pictures of turbos... they ain't really turbos. Well... kinda turbos. But they ARE astrea snails! I know... they're often called "turbo astrea" snails, but I think when most people talk about "turbos" they mean the big fat rounder shelled ones. More like this...